The escalating requirements for system capacity and higher gain over larger coverage areas have necessitated a corresponding increase in RF power transmission requirements of space-based antenna systems.
A high RF power radiating antenna suitable for use in an extraterrestrial environment is disclosed in commonly assigned U.S. Pat. No. 6,172,655 B1. Referring to FIGS. 1 (A) and 1 (B), the antenna 10 system disclosed therein includes a winding 12, a ground plane 14, and a coaxial feed. As illustrated, winding 12 includes an electrical conductor 20 helically wound about an axis 8 oriented orthogonal to a ground plane 14. Conductor 20 may be in the form of a solid or tubular (i.e., hollow) wire, or ribbon-shaped, etc., and typically is comprised of aluminum, copper, or an alloy thereof. Conductor 20 includes a first, or lower, end adjacent the ground plane 14 and a second, or upper, end remote from the ground plane 14. The antenna winding 12 is helically configured and includes a first, or lower, portion 22 and a second, or upper, portion 24. As illustrated, conductor 20 is formed as a single, continuous element, the first, or lower, and second, or upper portions 22 and 24 are immediately adjacent to each other and connect at location 28. The first, or lower, portion 22 of antenna winding 12, helically configured conductor 20 extends between planes 31 and 32 and is wound with a pitch angle α relative to plane 31 parallel to the upper surface of ground plane 14. The second, or upper portion 24 of antenna winding 12 extends between planes 32 and 33, includes upper (or distal) end 30, and the helically configured conductor 20 is wound in this portion with a pitch angle β relative to plane 32 which is parallel to plane 31 and includes location 28. As is evident from the figures, pitch angle β is greater than pitch angle α, i.e., the first, or lower, portion 22 of the helically configured conductor 20 is more tightly wound than the second, or upper, portion 24. The first, or lower, portion 22 of conductor 20 is wound or defined on the “surface” 41 of a section or segment of a first cone 41c, which cone segment is centered on axis 8, has its smaller diameter D1 coincident with plane 31 and its larger diameter D2 coincident with plane 32. The second, or upper, portion 24 of conductor 20 is wound or defined on the “surface” 42 of a second cone 42c, which cone segment is also centered on axis 8, has its smaller diameter D3 coincident with plane 33 and its larger diameter D2 coincident with plane 32. As is also evident from the figures, second cone 42c extends for a longer distance along central axis 8 than first cone 41c. 
Also as illustrated, feed end 26 of antenna winding 12 is connected the upper end of a center conductor 16c associated with coaxial feed 16. Antenna winding 12 is thus electrically insulated from ground plane 14.
RF power loss within the antenna element, especially at higher power levels, results in a local temperature increase within the RF radiating element, the temperature increase being greatest in the first, or lower, portion 22 proximal the interacting, RF reflecting ground plane 14 or other radiating structure. For example, depending upon the RF activating power, a temperature gradient of up to about 100° C. may be created between the first, or lower, portion 22 (i.e., the RF power feed portion) adjacent the ground plane 14 and the second, or upper, portion 24. Since the RF-generated thermal energy cannot be fully dissipated by the RF radiating element (e.g., of aluminum, copper, copper-plated aluminum, or other electrically conductive material or alloy), the localized heating and temperature differential can result in an excessively high temperature condition within the RF radiating element and/or supporting structure. Thus, operating temperatures can exceed the capability of the material(s) of the RF radiating element and/or the supporting structure.
Conventional approaches for providing heat sinking for mitigating negative effects arising from RF power loss in radiating elements in space vacuum environments typically involve thermal dissipation via conduction and radiation. Currently, such approaches rely upon thermal conduction along the RF radiating element, thermal conduction into the structural support, and direct thermal radiation from the radiating element to the space environment. One such approach comprises adding a thermally conductive dielectric material in the region of high RF loss of the radiating element and conductively coupling the material to the radiating element. Such arrangement can locally dissipate thermal energy generated from RF losses from the radiating element, providing there is intimate contact between the RF radiating element and a substantial mass or large area (e.g., an antenna ground plane) acting as a heat sink. In this instance, the thermal energy is transferred by conduction into the thermally conductive dielectric material and then into the mass (i.e., the ground plane in this example). However, this approach incurs a disadvantageous consequence in that the thermally conductive dielectric material has a negative effect on the RF matching of the antenna. According to another conventional approach, the size of the RF radiating element, e.g., the diameter, is increased, resulting in an increase in the thermal radiating area. However, the effect of the increase in the size of the RF radiating element must be considered when designing the antenna.
In view of the foregoing, there exists a clear need for improved means and methodology for mitigating the above-described problems, disadvantages, and drawbacks associated with the conventional approaches for providing dissipation of thermal energy arising from energy losses in radiating elements, e.g., RF radiating antennas, which means and methodology are fully compatible with the requirements for high RF power space-based or terrestrial applications.